The overall objective of this research is to identify the long term effects resulting from prenatal exposure to steroidal hormones in humans. The foci of these studies are the synthetic estrogen diethylstilbestrol (DES), which has been related to a rare form of vaginal cancer in young women and girls as well as genital abnormalities in male offspring; and the synthetic progestin 19-nor 17-alpha-ethinyltestosterone (19NET), the most androgenic and potent of the synthetic progestins causing masculinization of the external genitalia in approximately 18 percent of exposed female offspring. An attempt is being made to identify and elucidate the sequelae of exposure to DES and 19NET on the offspring of mothers administered these preparations during pregnancy. Evaluation is designed to test the possible effects on cognitive abilities, personality/temperament, brain laterlization, motor performance, and IQ in comparison to unexposed siblings. Parallel studies employing stringent experimental procedure and comparative methodology with mice, in which the control of dosage and timing schedules as well as the random assignment of subjects to groups is possible, are designed to produce precise deliniation of the effects of DES and 19NET on behavior and aspects of physiology. Further, the study of the laboratory animal permits the administration of hormone regimes which closely approximate those given humans, thereby enabling results from these experiments to be used both to generate suggestions for new avenues of inquiry in the research with humans as well as to assist in the interpretation of the data generated from the human subjects.